1. Field of the Invention
The present invention relates to a method for deciding a quantization scaling factor, and more particularly, to a method for deciding a quantization scaling factor based on the object edge strength and the flat area strength of the image.
2. Description of the Related Art
FIG. 1 schematically shows a block diagram of an image encoder with a bit rate controller 100. In order to control the data size, when the discrete cosine transform coefficients (DCT) are quantized by the image encoder, the quantizing steps need to be adjusted based on the quantization scaling factor (i.e. Q value), which is determined by the bit rate controller 100. Accordingly, the algorithm of generating the quantization scaling factor by the bit rate controller has significantly impact on the quality of the image compression.
In the prior art, the basic method of the bit rate controller is to increase the quality of image compression as much as possible in a predetermined data size. In recent years, visual mentality has been further considered, such that the distortion of the compressed image is not easily recognized by the viewer and the sensitive area of human eyes on the image quality is also appropriately improved. However, the items that can be detected and recognized by the visual mentality are still not versatile enough; and most of the detection items are just like bright or dark, simple or complex, fast moving or still picture, . . . , etc. How to integrate the detection of object edge and flat area, which are important to the visual mentality, into the process of image compression has not been developed.